Rain or Shine

jason WStamp Photo/Illustration Credits: Cover: Donna Day/Getty; p. 2, 6: Ortelius Design; p. 3: Getty Images, BARRY RUNK/STAN/Grant Heilman Photography; p. 4: Paul Seheult; Eye Ubiquitous/CORBIS, BARRY RUNK/Grant Heilman Photography, Jeff Greenberg/The Image Works; p. 5: Photos.com; p. 7: Graham Neden; Ecoscene/CORBIS; p. 8: CORBIS. Copyright © by Harcourt, Inc. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopy, recording, or any information storage and retrieval system, without permission in writing from the publisher. Requests for permission to make copies of any part of the work should be addressed to School Permissions and Copyrights, Harcourt, Inc., 6277 Sea Harbor Drive, Orlando, Florida 32887-6777. Fax: 407-345-2418. HARCOURT and the Harcourt Logo are trademarks of Harcourt, Inc., registered in the United States of America and/or other jurisdictions. Printed in the United States of America ISBN 0-15-344006-6 1 2 3 4 5 6 7 8 9 10 175 10 09 08 07 06 05 Visit The Learning Site! www.harcourtschool.com Orlando Austin New York San Diego Toronto London by Mary Dylewski jason BStamp 2 Introduction Weather can change from minute to minute, hour to hour, day to day, or season to season. Meteorologists are scientists who study Earth’s atmosphere in order to predict these changes. Meteorologists use many kinds of instruments to gather data. Some of these instruments are on land. Others are at sea. Still others are high above Earth. The data gathered with these tools is often used to make weather maps, like the one shown here. H H LL Flurries Snow Ice Sunny Partly Cloudy Cloudy L H High Pressure Low Pressure FRONTS TEMPERATURE Cold Warm Stationary Showers Thunderstorms Rain -10s -0s 0s 10s 20s 30s 40s 50s 60s 70s 80s 90s 100s Harcourt School Publishers Preface/Anthology Rain or Shine, Grade 2 4/C CXEFL07ARD29_ALR_1 A Weather Map 1st proof jason Main_Bstamp jason Main_Bstamp Thermometers A thermometer is a tool that measures air temperature. Most thermometers are glass tubes that are about half full of liquid. The liquid in the tube rises when air warms. The liquid falls when air cools. A thermometer measures temperature in degrees. Rain Gauges A rain gauge is a container that measures the amount of rain that falls within a given time. A scale on the container shows the amount of rain in inches. measures air temperature. Most thermometers are glass tubes that are about half full of liquid. The 3 jason Main_Bstamp jason Main_Bstamp 4 Barometers A barometer measures air pressure in inches of mercury or millibars. Changes in air pressure are clues to future weather conditions. A drop in air pressure can mean bad weather. A rise in pressure can mean that good weather lies ahead. Anemometers and Wind Vanes An anemometer uses spinning cups to measure wind speed in miles per hour. A wind vane shows wind direction. If a wind vane points north, the wind is moving from the north to the south. future weather conditions. jason Main_Bstamp jason Main_Bstamp jason Main_Bstamp 5 Measuring Humidity Humidity is the amount of water vapor in the air. Water vapor is the gaseous form of water. The amount of this invisible gas in the air can vary. Dry air, for example, has little water vapor in it. Very humid air can hold up to about 4 percent water vapor. A hygrometer measures humidity. Some hygrometers use either mirrors or a piece of hair to measure humidity. A psychrometer is a hygrometer that uses two thermometers to measure water vapor. One thermometer is dry. The other is wet. The two temperatures are compared to fi nd humidity. dry. The other is wet. The two temperatures are compared to fi nd humidity. jason Main_Bstamp jason Main_Bstamp jason Main_Bstamp 6 Harcourt School Publishers Preface/Anthology Rain or Shine, Grade 2 4/C CXEFL07ARD29_ALR_9A Radar dish and snowflake 2nd proof Radar Meteorologists use radar to find and measure precipitation. A radar dish sends out energy as waves. When the waves hit an object such as a raindrop or a snowflake, they scatter. Some of the energy bounces back to the radar dish. Then computers analyze the strength of the energy and the time it took it to return. These data help meteorologists locate storms and tell how quickly they are moving. Then meteorologists can warn people to prepare for the storms. jason Main_Bstamp jason Main_Bstamp Weather Balloons Weather balloons were first used in France in 1892. These balloons are still important tools that gather data in order to predict the weather. Weather balloons float high into the atmosphere. Some rise to heights of more than 20 miles above Earth! Some weather balloons stay in one place as instruments on board gather data. Other balloons drift through the air to collect information. When a weather balloon bursts, a small parachute carries the balloon’s instruments safely back to Earth. D Weather balloons are launched from many places around the world twice each day at the same time. Instruments collect data about Earth’s atmosphere. 7 jason Main_Bstamp jason Main_Bstamp jason Main_Wstamp 8 Other Important Tools A satellite is an object that orbits Earth. Weather satellites gather data on clouds, wind, sunshine, and precipitation. The newest satellites gather more information and gather data much more quickly than older satellites. Computers are important tools for studying and forecasting weather. They quickly gather and process data. Meteorologists from all across the world use computers to share weather data. jason Main_Bstamp jason Main_Bstamp Think and Respond 1. What does a meteorologist do? 2. What is a barometer? What does it measure? 3. How is radar used to predict the weather? 4. Expository Write a paragraph telling how weather balloons and weather satellites are the same or different. Hands-On Activity Weather Changes Make a chart to record weather data for your city or town for one week. Tell how the weather changed. School-Home Connection Catch the Wind With a family member, use books or the Internet to find out how to make a simple anemometer. Use your instrument on a windy day to see how fast the wind is blowing. jason Main_Bstamp jason Main_Bstamp jason Main_Bstamp jason Main_Bstamp jason Main_Bstamp jason Main_Bstamp jason Main_Bstamp